This study would determine the feasibility of producing a combination Seldinger catheter/insertion sheath from their softenable, shape-memory thermoplastic (SMT). This device would simplify insertion of venous and arterial catheters by combining puncture, dilation and sheath placement in a single device. The SMT would be compounded and pelletized, then extruded as a high modulus, thin-walled, radiopaque tube, which will be post-formed to have an approximately 16 gauge distal tip. The remainder of the catheter body would be French 8 or larger. Upon reaching 37 degrees C, the tapered tip would expand to the larger diameter of the proximal end of the sheath, to permit catheter insertion with an optional guide wire. During expansion, the SMT will undergo a stiffness reduction, which should help reduce intimal damage and thrombosis. This work will use in vitro simulation of catheter insertion, and will stress material and process optimization of SMT polymers for use in implantable medical devices, including catheters of more complex design. The shape-memory Seldinger catheter/sheath, to be fully developed in Phase II, should be useful for rapid insertion of a variety of diagnostic and therapeutic devices, including radiography catheters, intraaortic balloons, femoral shunts angioplasty devices and catheter-mounted blood pumps.